Dental restorations are created by a number of techniques. One particularly popular technique is the pressable technique in which a ceramic ingot is heated and pressed using the lost wax process to create a dental restoration that can be permanently placed in a patient's mouth.
Natural and artificial teeth come in a variety colors. If a dental restoration does not match very closely to a patient's natural tooth color, the fact that the patient has a restoration is readily apparent. This is undesirable because it does not produce the aesthetically pleasing result sought by many dental patients.
Shade guides have been developed that establish a finite number of shades to which a patient's tooth can be matched so that a suitable restoration can be produced. One particularly popular and still widely used shade guide is the Vita® Classic shade guide introduced in 1956 by Vita Zahnfabrik AG of Germany. The Vita Classic shade guide consists of 16 separate shades divided by hue into four families identified as A through D. Each family is then further divided into four subdivisions, each numbered 1 through 4. The subdivisions are numbered in order of decreasing value (lightness or darkness) and increasing chroma (intensity of color).
Current pressable dental restoration systems generally require using a different shade of ingot for each of the different shades represented on shade guide. While this gives a satisfactory final restoration product, it is inefficient for dental laboratories that make the restorations. For example, dental laboratories must keep a ready inventory of ingots for each of the 16 shades represented by the Vita Classic shade guide on hand, many of which are less popular than others. A glaze is then usually applied and fired to the restoration to impart a glassy appearance.
Other existing pressable restoration systems provide a limited number of neutral colored ingots to which two, three or more layers of low chroma shade stain must be applied and fired instead of glazing. While this may reduce the inventory of ingot types needed by a laboratory, this process still lacks efficiency because the neutral ingots do not correspond to any shades of the shade guide; thus the restoration must always be stained to achieve the desired end result. Additionally, staining may result in a slightly less aesthetic restoration than restorations that are glazed over an already properly shaded restoration.
What is needed is a more efficient method for making dental restorations that correspond to the shade of a patient's tooth that reduces a laboratory's need for a full set of different shades of ingots in its on-hand inventory, while still providing a high percentage of restorations that can be glazed as part of the finishing process.
What is also needed is a more efficient method for making those dental restorations that do need to be stained, avoiding the need for applying and firing multiple layers of stains.